1. Field of the Invention
The present invention relates to a pneumatic tire in which both steering stability and riding comfort are enhanced by specifying viscoelasticity characteristics of a carcass cord.
2. Description of the Related Art
Conventionally, organic fiber cords such as nylon, rayon, polyethylene terephthalate (PET) and the like are widely used as a carcass cord of a pneumatic tire for a passenger car and an automatic two-wheel vehicle. Especially, the PET fiber cord is going mainstream of the carcass cord in views of tire rigidity, size stability of tire, flat spot resistance and the like. However, since modulus of the PET fiber cord at a high temperature is largely deteriorated, steering stability at the time of high speed running is poor. Further, as the performance of a vehicle is enhanced and the speed is increased, performance required for a tire becomes stricter, and in recent years, it is strongly required to further enhance the steering stability at high speed running.
In recent years, it is proposed to use a fiber cord having higher elasticity than that of the PET fiber cord as a carcass cord. However, if the elasticity of the carcass cord is increased, the tire rigidity is increased so that the steering stability at high speed running is enhanced, but there is a problem that the riding comfort is deteriorated.